<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>title</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        html,
        body {
            min-width: 1100px;
            height: 100%;
        }
        body{
            font-size: 16px;
        }

        .title {
            height: 100px;
            background-color: antiquewhite;
            text-align: center;
            line-height: 100px;
        }

        .x {
            width: 100rem;
            height: 10rem;
            background-color: yellow;
        }
    </style>
</head>

<body>
    <div class="title">这是标题</div>
    <div class="x"></div>
</body>
<script>
    (function () {
        function setRootFontSize() {
            let rem, rootWidth;
            let rootHtml = document.documentElement;
            //限制展现页面的最小宽度
            rootWidth = Math.max(rootHtml.clientWidth, 1100);
            // 19.2 = 设计图尺寸宽 / 100（ 设计图的rem = 100 ）
            rem = rootWidth / 100;
            // 动态写入样式
            rootHtml.style.fontSize = `${rem}px`;
        }
        setRootFontSize();
        window.addEventListener("resize", setRootFontSize, false);
    })();
</script>

</html>